1 /* 2 * Copyright (C) 2009 Red Hat, Inc. 3 * 4 * This work is licensed under the terms of the GNU GPL, version 2. See 5 * the COPYING file in the top-level directory. 6 */ 7 8 #include <linux/mm.h> 9 #include <linux/sched.h> 10 #include <linux/highmem.h> 11 #include <linux/hugetlb.h> 12 #include <linux/mmu_notifier.h> 13 #include <linux/rmap.h> 14 #include <linux/swap.h> 15 #include <linux/shrinker.h> 16 #include <linux/mm_inline.h> 17 #include <linux/kthread.h> 18 #include <linux/khugepaged.h> 19 #include <linux/freezer.h> 20 #include <linux/mman.h> 21 #include <linux/pagemap.h> 22 #include <linux/migrate.h> 23 24 #include <asm/tlb.h> 25 #include <asm/pgalloc.h> 26 #include "internal.h" 27 28 /* 29 * By default transparent hugepage support is enabled for all mappings 30 * and khugepaged scans all mappings. Defrag is only invoked by 31 * khugepaged hugepage allocations and by page faults inside 32 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived 33 * allocations. 34 */ 35 unsigned long transparent_hugepage_flags __read_mostly = 36 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 37 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 38 #endif 39 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 40 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 41 #endif 42 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)| 43 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| 44 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 45 46 /* default scan 8*512 pte (or vmas) every 30 second */ 47 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; 48 static unsigned int khugepaged_pages_collapsed; 49 static unsigned int khugepaged_full_scans; 50 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 51 /* during fragmentation poll the hugepage allocator once every minute */ 52 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 53 static struct task_struct *khugepaged_thread __read_mostly; 54 static DEFINE_MUTEX(khugepaged_mutex); 55 static DEFINE_SPINLOCK(khugepaged_mm_lock); 56 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 57 /* 58 * default collapse hugepages if there is at least one pte mapped like 59 * it would have happened if the vma was large enough during page 60 * fault. 61 */ 62 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; 63 64 static int khugepaged(void *none); 65 static int mm_slots_hash_init(void); 66 static int khugepaged_slab_init(void); 67 static void khugepaged_slab_free(void); 68 69 #define MM_SLOTS_HASH_HEADS 1024 70 static struct hlist_head *mm_slots_hash __read_mostly; 71 static struct kmem_cache *mm_slot_cache __read_mostly; 72 73 /** 74 * struct mm_slot - hash lookup from mm to mm_slot 75 * @hash: hash collision list 76 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 77 * @mm: the mm that this information is valid for 78 */ 79 struct mm_slot { 80 struct hlist_node hash; 81 struct list_head mm_node; 82 struct mm_struct *mm; 83 }; 84 85 /** 86 * struct khugepaged_scan - cursor for scanning 87 * @mm_head: the head of the mm list to scan 88 * @mm_slot: the current mm_slot we are scanning 89 * @address: the next address inside that to be scanned 90 * 91 * There is only the one khugepaged_scan instance of this cursor structure. 92 */ 93 struct khugepaged_scan { 94 struct list_head mm_head; 95 struct mm_slot *mm_slot; 96 unsigned long address; 97 }; 98 static struct khugepaged_scan khugepaged_scan = { 99 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 100 }; 101 102 103 static int set_recommended_min_free_kbytes(void) 104 { 105 struct zone *zone; 106 int nr_zones = 0; 107 unsigned long recommended_min; 108 extern int min_free_kbytes; 109 110 if (!khugepaged_enabled()) 111 return 0; 112 113 for_each_populated_zone(zone) 114 nr_zones++; 115 116 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */ 117 recommended_min = pageblock_nr_pages * nr_zones * 2; 118 119 /* 120 * Make sure that on average at least two pageblocks are almost free 121 * of another type, one for a migratetype to fall back to and a 122 * second to avoid subsequent fallbacks of other types There are 3 123 * MIGRATE_TYPES we care about. 124 */ 125 recommended_min += pageblock_nr_pages * nr_zones * 126 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 127 128 /* don't ever allow to reserve more than 5% of the lowmem */ 129 recommended_min = min(recommended_min, 130 (unsigned long) nr_free_buffer_pages() / 20); 131 recommended_min <<= (PAGE_SHIFT-10); 132 133 if (recommended_min > min_free_kbytes) 134 min_free_kbytes = recommended_min; 135 setup_per_zone_wmarks(); 136 return 0; 137 } 138 late_initcall(set_recommended_min_free_kbytes); 139 140 static int start_khugepaged(void) 141 { 142 int err = 0; 143 if (khugepaged_enabled()) { 144 if (!khugepaged_thread) 145 khugepaged_thread = kthread_run(khugepaged, NULL, 146 "khugepaged"); 147 if (unlikely(IS_ERR(khugepaged_thread))) { 148 printk(KERN_ERR 149 "khugepaged: kthread_run(khugepaged) failed\n"); 150 err = PTR_ERR(khugepaged_thread); 151 khugepaged_thread = NULL; 152 } 153 154 if (!list_empty(&khugepaged_scan.mm_head)) 155 wake_up_interruptible(&khugepaged_wait); 156 157 set_recommended_min_free_kbytes(); 158 } else if (khugepaged_thread) { 159 kthread_stop(khugepaged_thread); 160 khugepaged_thread = NULL; 161 } 162 163 return err; 164 } 165 166 static atomic_t huge_zero_refcount; 167 static unsigned long huge_zero_pfn __read_mostly; 168 169 static inline bool is_huge_zero_pfn(unsigned long pfn) 170 { 171 unsigned long zero_pfn = ACCESS_ONCE(huge_zero_pfn); 172 return zero_pfn && pfn == zero_pfn; 173 } 174 175 static inline bool is_huge_zero_pmd(pmd_t pmd) 176 { 177 return is_huge_zero_pfn(pmd_pfn(pmd)); 178 } 179 180 static unsigned long get_huge_zero_page(void) 181 { 182 struct page *zero_page; 183 retry: 184 if (likely(atomic_inc_not_zero(&huge_zero_refcount))) 185 return ACCESS_ONCE(huge_zero_pfn); 186 187 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, 188 HPAGE_PMD_ORDER); 189 if (!zero_page) { 190 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); 191 return 0; 192 } 193 count_vm_event(THP_ZERO_PAGE_ALLOC); 194 preempt_disable(); 195 if (cmpxchg(&huge_zero_pfn, 0, page_to_pfn(zero_page))) { 196 preempt_enable(); 197 __free_page(zero_page); 198 goto retry; 199 } 200 201 /* We take additional reference here. It will be put back by shrinker */ 202 atomic_set(&huge_zero_refcount, 2); 203 preempt_enable(); 204 return ACCESS_ONCE(huge_zero_pfn); 205 } 206 207 static void put_huge_zero_page(void) 208 { 209 /* 210 * Counter should never go to zero here. Only shrinker can put 211 * last reference. 212 */ 213 BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); 214 } 215 216 static int shrink_huge_zero_page(struct shrinker *shrink, 217 struct shrink_control *sc) 218 { 219 if (!sc->nr_to_scan) 220 /* we can free zero page only if last reference remains */ 221 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; 222 223 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { 224 unsigned long zero_pfn = xchg(&huge_zero_pfn, 0); 225 BUG_ON(zero_pfn == 0); 226 __free_page(__pfn_to_page(zero_pfn)); 227 } 228 229 return 0; 230 } 231 232 static struct shrinker huge_zero_page_shrinker = { 233 .shrink = shrink_huge_zero_page, 234 .seeks = DEFAULT_SEEKS, 235 }; 236 237 #ifdef CONFIG_SYSFS 238 239 static ssize_t double_flag_show(struct kobject *kobj, 240 struct kobj_attribute *attr, char *buf, 241 enum transparent_hugepage_flag enabled, 242 enum transparent_hugepage_flag req_madv) 243 { 244 if (test_bit(enabled, &transparent_hugepage_flags)) { 245 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); 246 return sprintf(buf, "[always] madvise never\n"); 247 } else if (test_bit(req_madv, &transparent_hugepage_flags)) 248 return sprintf(buf, "always [madvise] never\n"); 249 else 250 return sprintf(buf, "always madvise [never]\n"); 251 } 252 static ssize_t double_flag_store(struct kobject *kobj, 253 struct kobj_attribute *attr, 254 const char *buf, size_t count, 255 enum transparent_hugepage_flag enabled, 256 enum transparent_hugepage_flag req_madv) 257 { 258 if (!memcmp("always", buf, 259 min(sizeof("always")-1, count))) { 260 set_bit(enabled, &transparent_hugepage_flags); 261 clear_bit(req_madv, &transparent_hugepage_flags); 262 } else if (!memcmp("madvise", buf, 263 min(sizeof("madvise")-1, count))) { 264 clear_bit(enabled, &transparent_hugepage_flags); 265 set_bit(req_madv, &transparent_hugepage_flags); 266 } else if (!memcmp("never", buf, 267 min(sizeof("never")-1, count))) { 268 clear_bit(enabled, &transparent_hugepage_flags); 269 clear_bit(req_madv, &transparent_hugepage_flags); 270 } else 271 return -EINVAL; 272 273 return count; 274 } 275 276 static ssize_t enabled_show(struct kobject *kobj, 277 struct kobj_attribute *attr, char *buf) 278 { 279 return double_flag_show(kobj, attr, buf, 280 TRANSPARENT_HUGEPAGE_FLAG, 281 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 282 } 283 static ssize_t enabled_store(struct kobject *kobj, 284 struct kobj_attribute *attr, 285 const char *buf, size_t count) 286 { 287 ssize_t ret; 288 289 ret = double_flag_store(kobj, attr, buf, count, 290 TRANSPARENT_HUGEPAGE_FLAG, 291 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 292 293 if (ret > 0) { 294 int err; 295 296 mutex_lock(&khugepaged_mutex); 297 err = start_khugepaged(); 298 mutex_unlock(&khugepaged_mutex); 299 300 if (err) 301 ret = err; 302 } 303 304 return ret; 305 } 306 static struct kobj_attribute enabled_attr = 307 __ATTR(enabled, 0644, enabled_show, enabled_store); 308 309 static ssize_t single_flag_show(struct kobject *kobj, 310 struct kobj_attribute *attr, char *buf, 311 enum transparent_hugepage_flag flag) 312 { 313 return sprintf(buf, "%d\n", 314 !!test_bit(flag, &transparent_hugepage_flags)); 315 } 316 317 static ssize_t single_flag_store(struct kobject *kobj, 318 struct kobj_attribute *attr, 319 const char *buf, size_t count, 320 enum transparent_hugepage_flag flag) 321 { 322 unsigned long value; 323 int ret; 324 325 ret = kstrtoul(buf, 10, &value); 326 if (ret < 0) 327 return ret; 328 if (value > 1) 329 return -EINVAL; 330 331 if (value) 332 set_bit(flag, &transparent_hugepage_flags); 333 else 334 clear_bit(flag, &transparent_hugepage_flags); 335 336 return count; 337 } 338 339 /* 340 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 341 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 342 * memory just to allocate one more hugepage. 343 */ 344 static ssize_t defrag_show(struct kobject *kobj, 345 struct kobj_attribute *attr, char *buf) 346 { 347 return double_flag_show(kobj, attr, buf, 348 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 349 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 350 } 351 static ssize_t defrag_store(struct kobject *kobj, 352 struct kobj_attribute *attr, 353 const char *buf, size_t count) 354 { 355 return double_flag_store(kobj, attr, buf, count, 356 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 357 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 358 } 359 static struct kobj_attribute defrag_attr = 360 __ATTR(defrag, 0644, defrag_show, defrag_store); 361 362 static ssize_t use_zero_page_show(struct kobject *kobj, 363 struct kobj_attribute *attr, char *buf) 364 { 365 return single_flag_show(kobj, attr, buf, 366 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 367 } 368 static ssize_t use_zero_page_store(struct kobject *kobj, 369 struct kobj_attribute *attr, const char *buf, size_t count) 370 { 371 return single_flag_store(kobj, attr, buf, count, 372 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 373 } 374 static struct kobj_attribute use_zero_page_attr = 375 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); 376 #ifdef CONFIG_DEBUG_VM 377 static ssize_t debug_cow_show(struct kobject *kobj, 378 struct kobj_attribute *attr, char *buf) 379 { 380 return single_flag_show(kobj, attr, buf, 381 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 382 } 383 static ssize_t debug_cow_store(struct kobject *kobj, 384 struct kobj_attribute *attr, 385 const char *buf, size_t count) 386 { 387 return single_flag_store(kobj, attr, buf, count, 388 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 389 } 390 static struct kobj_attribute debug_cow_attr = 391 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 392 #endif /* CONFIG_DEBUG_VM */ 393 394 static struct attribute *hugepage_attr[] = { 395 &enabled_attr.attr, 396 &defrag_attr.attr, 397 &use_zero_page_attr.attr, 398 #ifdef CONFIG_DEBUG_VM 399 &debug_cow_attr.attr, 400 #endif 401 NULL, 402 }; 403 404 static struct attribute_group hugepage_attr_group = { 405 .attrs = hugepage_attr, 406 }; 407 408 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 409 struct kobj_attribute *attr, 410 char *buf) 411 { 412 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 413 } 414 415 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 416 struct kobj_attribute *attr, 417 const char *buf, size_t count) 418 { 419 unsigned long msecs; 420 int err; 421 422 err = strict_strtoul(buf, 10, &msecs); 423 if (err || msecs > UINT_MAX) 424 return -EINVAL; 425 426 khugepaged_scan_sleep_millisecs = msecs; 427 wake_up_interruptible(&khugepaged_wait); 428 429 return count; 430 } 431 static struct kobj_attribute scan_sleep_millisecs_attr = 432 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 433 scan_sleep_millisecs_store); 434 435 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 436 struct kobj_attribute *attr, 437 char *buf) 438 { 439 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 440 } 441 442 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 443 struct kobj_attribute *attr, 444 const char *buf, size_t count) 445 { 446 unsigned long msecs; 447 int err; 448 449 err = strict_strtoul(buf, 10, &msecs); 450 if (err || msecs > UINT_MAX) 451 return -EINVAL; 452 453 khugepaged_alloc_sleep_millisecs = msecs; 454 wake_up_interruptible(&khugepaged_wait); 455 456 return count; 457 } 458 static struct kobj_attribute alloc_sleep_millisecs_attr = 459 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 460 alloc_sleep_millisecs_store); 461 462 static ssize_t pages_to_scan_show(struct kobject *kobj, 463 struct kobj_attribute *attr, 464 char *buf) 465 { 466 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 467 } 468 static ssize_t pages_to_scan_store(struct kobject *kobj, 469 struct kobj_attribute *attr, 470 const char *buf, size_t count) 471 { 472 int err; 473 unsigned long pages; 474 475 err = strict_strtoul(buf, 10, &pages); 476 if (err || !pages || pages > UINT_MAX) 477 return -EINVAL; 478 479 khugepaged_pages_to_scan = pages; 480 481 return count; 482 } 483 static struct kobj_attribute pages_to_scan_attr = 484 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 485 pages_to_scan_store); 486 487 static ssize_t pages_collapsed_show(struct kobject *kobj, 488 struct kobj_attribute *attr, 489 char *buf) 490 { 491 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 492 } 493 static struct kobj_attribute pages_collapsed_attr = 494 __ATTR_RO(pages_collapsed); 495 496 static ssize_t full_scans_show(struct kobject *kobj, 497 struct kobj_attribute *attr, 498 char *buf) 499 { 500 return sprintf(buf, "%u\n", khugepaged_full_scans); 501 } 502 static struct kobj_attribute full_scans_attr = 503 __ATTR_RO(full_scans); 504 505 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 506 struct kobj_attribute *attr, char *buf) 507 { 508 return single_flag_show(kobj, attr, buf, 509 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 510 } 511 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 512 struct kobj_attribute *attr, 513 const char *buf, size_t count) 514 { 515 return single_flag_store(kobj, attr, buf, count, 516 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 517 } 518 static struct kobj_attribute khugepaged_defrag_attr = 519 __ATTR(defrag, 0644, khugepaged_defrag_show, 520 khugepaged_defrag_store); 521 522 /* 523 * max_ptes_none controls if khugepaged should collapse hugepages over 524 * any unmapped ptes in turn potentially increasing the memory 525 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 526 * reduce the available free memory in the system as it 527 * runs. Increasing max_ptes_none will instead potentially reduce the 528 * free memory in the system during the khugepaged scan. 529 */ 530 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 531 struct kobj_attribute *attr, 532 char *buf) 533 { 534 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 535 } 536 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 537 struct kobj_attribute *attr, 538 const char *buf, size_t count) 539 { 540 int err; 541 unsigned long max_ptes_none; 542 543 err = strict_strtoul(buf, 10, &max_ptes_none); 544 if (err || max_ptes_none > HPAGE_PMD_NR-1) 545 return -EINVAL; 546 547 khugepaged_max_ptes_none = max_ptes_none; 548 549 return count; 550 } 551 static struct kobj_attribute khugepaged_max_ptes_none_attr = 552 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 553 khugepaged_max_ptes_none_store); 554 555 static struct attribute *khugepaged_attr[] = { 556 &khugepaged_defrag_attr.attr, 557 &khugepaged_max_ptes_none_attr.attr, 558 &pages_to_scan_attr.attr, 559 &pages_collapsed_attr.attr, 560 &full_scans_attr.attr, 561 &scan_sleep_millisecs_attr.attr, 562 &alloc_sleep_millisecs_attr.attr, 563 NULL, 564 }; 565 566 static struct attribute_group khugepaged_attr_group = { 567 .attrs = khugepaged_attr, 568 .name = "khugepaged", 569 }; 570 571 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 572 { 573 int err; 574 575 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 576 if (unlikely(!*hugepage_kobj)) { 577 printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n"); 578 return -ENOMEM; 579 } 580 581 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 582 if (err) { 583 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n"); 584 goto delete_obj; 585 } 586 587 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 588 if (err) { 589 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n"); 590 goto remove_hp_group; 591 } 592 593 return 0; 594 595 remove_hp_group: 596 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 597 delete_obj: 598 kobject_put(*hugepage_kobj); 599 return err; 600 } 601 602 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 603 { 604 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 605 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 606 kobject_put(hugepage_kobj); 607 } 608 #else 609 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 610 { 611 return 0; 612 } 613 614 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 615 { 616 } 617 #endif /* CONFIG_SYSFS */ 618 619 static int __init hugepage_init(void) 620 { 621 int err; 622 struct kobject *hugepage_kobj; 623 624 if (!has_transparent_hugepage()) { 625 transparent_hugepage_flags = 0; 626 return -EINVAL; 627 } 628 629 err = hugepage_init_sysfs(&hugepage_kobj); 630 if (err) 631 return err; 632 633 err = khugepaged_slab_init(); 634 if (err) 635 goto out; 636 637 err = mm_slots_hash_init(); 638 if (err) { 639 khugepaged_slab_free(); 640 goto out; 641 } 642 643 register_shrinker(&huge_zero_page_shrinker); 644 645 /* 646 * By default disable transparent hugepages on smaller systems, 647 * where the extra memory used could hurt more than TLB overhead 648 * is likely to save. The admin can still enable it through /sys. 649 */ 650 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) 651 transparent_hugepage_flags = 0; 652 653 start_khugepaged(); 654 655 return 0; 656 out: 657 hugepage_exit_sysfs(hugepage_kobj); 658 return err; 659 } 660 module_init(hugepage_init) 661 662 static int __init setup_transparent_hugepage(char *str) 663 { 664 int ret = 0; 665 if (!str) 666 goto out; 667 if (!strcmp(str, "always")) { 668 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 669 &transparent_hugepage_flags); 670 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 671 &transparent_hugepage_flags); 672 ret = 1; 673 } else if (!strcmp(str, "madvise")) { 674 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 675 &transparent_hugepage_flags); 676 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 677 &transparent_hugepage_flags); 678 ret = 1; 679 } else if (!strcmp(str, "never")) { 680 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 681 &transparent_hugepage_flags); 682 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 683 &transparent_hugepage_flags); 684 ret = 1; 685 } 686 out: 687 if (!ret) 688 printk(KERN_WARNING 689 "transparent_hugepage= cannot parse, ignored\n"); 690 return ret; 691 } 692 __setup("transparent_hugepage=", setup_transparent_hugepage); 693 694 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 695 { 696 if (likely(vma->vm_flags & VM_WRITE)) 697 pmd = pmd_mkwrite(pmd); 698 return pmd; 699 } 700 701 static inline pmd_t mk_huge_pmd(struct page *page, struct vm_area_struct *vma) 702 { 703 pmd_t entry; 704 entry = mk_pmd(page, vma->vm_page_prot); 705 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 706 entry = pmd_mkhuge(entry); 707 return entry; 708 } 709 710 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, 711 struct vm_area_struct *vma, 712 unsigned long haddr, pmd_t *pmd, 713 struct page *page) 714 { 715 pgtable_t pgtable; 716 717 VM_BUG_ON(!PageCompound(page)); 718 pgtable = pte_alloc_one(mm, haddr); 719 if (unlikely(!pgtable)) 720 return VM_FAULT_OOM; 721 722 clear_huge_page(page, haddr, HPAGE_PMD_NR); 723 __SetPageUptodate(page); 724 725 spin_lock(&mm->page_table_lock); 726 if (unlikely(!pmd_none(*pmd))) { 727 spin_unlock(&mm->page_table_lock); 728 mem_cgroup_uncharge_page(page); 729 put_page(page); 730 pte_free(mm, pgtable); 731 } else { 732 pmd_t entry; 733 entry = mk_huge_pmd(page, vma); 734 /* 735 * The spinlocking to take the lru_lock inside 736 * page_add_new_anon_rmap() acts as a full memory 737 * barrier to be sure clear_huge_page writes become 738 * visible after the set_pmd_at() write. 739 */ 740 page_add_new_anon_rmap(page, vma, haddr); 741 set_pmd_at(mm, haddr, pmd, entry); 742 pgtable_trans_huge_deposit(mm, pgtable); 743 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 744 mm->nr_ptes++; 745 spin_unlock(&mm->page_table_lock); 746 } 747 748 return 0; 749 } 750 751 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) 752 { 753 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; 754 } 755 756 static inline struct page *alloc_hugepage_vma(int defrag, 757 struct vm_area_struct *vma, 758 unsigned long haddr, int nd, 759 gfp_t extra_gfp) 760 { 761 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp), 762 HPAGE_PMD_ORDER, vma, haddr, nd); 763 } 764 765 #ifndef CONFIG_NUMA 766 static inline struct page *alloc_hugepage(int defrag) 767 { 768 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 769 HPAGE_PMD_ORDER); 770 } 771 #endif 772 773 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, 774 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, 775 unsigned long zero_pfn) 776 { 777 pmd_t entry; 778 if (!pmd_none(*pmd)) 779 return false; 780 entry = pfn_pmd(zero_pfn, vma->vm_page_prot); 781 entry = pmd_wrprotect(entry); 782 entry = pmd_mkhuge(entry); 783 set_pmd_at(mm, haddr, pmd, entry); 784 pgtable_trans_huge_deposit(mm, pgtable); 785 mm->nr_ptes++; 786 return true; 787 } 788 789 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 790 unsigned long address, pmd_t *pmd, 791 unsigned int flags) 792 { 793 struct page *page; 794 unsigned long haddr = address & HPAGE_PMD_MASK; 795 pte_t *pte; 796 797 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { 798 if (unlikely(anon_vma_prepare(vma))) 799 return VM_FAULT_OOM; 800 if (unlikely(khugepaged_enter(vma))) 801 return VM_FAULT_OOM; 802 if (!(flags & FAULT_FLAG_WRITE) && 803 transparent_hugepage_use_zero_page()) { 804 pgtable_t pgtable; 805 unsigned long zero_pfn; 806 bool set; 807 pgtable = pte_alloc_one(mm, haddr); 808 if (unlikely(!pgtable)) 809 return VM_FAULT_OOM; 810 zero_pfn = get_huge_zero_page(); 811 if (unlikely(!zero_pfn)) { 812 pte_free(mm, pgtable); 813 count_vm_event(THP_FAULT_FALLBACK); 814 goto out; 815 } 816 spin_lock(&mm->page_table_lock); 817 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, 818 zero_pfn); 819 spin_unlock(&mm->page_table_lock); 820 if (!set) { 821 pte_free(mm, pgtable); 822 put_huge_zero_page(); 823 } 824 return 0; 825 } 826 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 827 vma, haddr, numa_node_id(), 0); 828 if (unlikely(!page)) { 829 count_vm_event(THP_FAULT_FALLBACK); 830 goto out; 831 } 832 count_vm_event(THP_FAULT_ALLOC); 833 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { 834 put_page(page); 835 goto out; 836 } 837 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, 838 page))) { 839 mem_cgroup_uncharge_page(page); 840 put_page(page); 841 goto out; 842 } 843 844 return 0; 845 } 846 out: 847 /* 848 * Use __pte_alloc instead of pte_alloc_map, because we can't 849 * run pte_offset_map on the pmd, if an huge pmd could 850 * materialize from under us from a different thread. 851 */ 852 if (unlikely(pmd_none(*pmd)) && 853 unlikely(__pte_alloc(mm, vma, pmd, address))) 854 return VM_FAULT_OOM; 855 /* if an huge pmd materialized from under us just retry later */ 856 if (unlikely(pmd_trans_huge(*pmd))) 857 return 0; 858 /* 859 * A regular pmd is established and it can't morph into a huge pmd 860 * from under us anymore at this point because we hold the mmap_sem 861 * read mode and khugepaged takes it in write mode. So now it's 862 * safe to run pte_offset_map(). 863 */ 864 pte = pte_offset_map(pmd, address); 865 return handle_pte_fault(mm, vma, address, pte, pmd, flags); 866 } 867 868 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 869 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 870 struct vm_area_struct *vma) 871 { 872 struct page *src_page; 873 pmd_t pmd; 874 pgtable_t pgtable; 875 int ret; 876 877 ret = -ENOMEM; 878 pgtable = pte_alloc_one(dst_mm, addr); 879 if (unlikely(!pgtable)) 880 goto out; 881 882 spin_lock(&dst_mm->page_table_lock); 883 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); 884 885 ret = -EAGAIN; 886 pmd = *src_pmd; 887 if (unlikely(!pmd_trans_huge(pmd))) { 888 pte_free(dst_mm, pgtable); 889 goto out_unlock; 890 } 891 /* 892 * mm->page_table_lock is enough to be sure that huge zero pmd is not 893 * under splitting since we don't split the page itself, only pmd to 894 * a page table. 895 */ 896 if (is_huge_zero_pmd(pmd)) { 897 unsigned long zero_pfn; 898 bool set; 899 /* 900 * get_huge_zero_page() will never allocate a new page here, 901 * since we already have a zero page to copy. It just takes a 902 * reference. 903 */ 904 zero_pfn = get_huge_zero_page(); 905 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 906 zero_pfn); 907 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ 908 ret = 0; 909 goto out_unlock; 910 } 911 if (unlikely(pmd_trans_splitting(pmd))) { 912 /* split huge page running from under us */ 913 spin_unlock(&src_mm->page_table_lock); 914 spin_unlock(&dst_mm->page_table_lock); 915 pte_free(dst_mm, pgtable); 916 917 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 918 goto out; 919 } 920 src_page = pmd_page(pmd); 921 VM_BUG_ON(!PageHead(src_page)); 922 get_page(src_page); 923 page_dup_rmap(src_page); 924 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 925 926 pmdp_set_wrprotect(src_mm, addr, src_pmd); 927 pmd = pmd_mkold(pmd_wrprotect(pmd)); 928 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 929 pgtable_trans_huge_deposit(dst_mm, pgtable); 930 dst_mm->nr_ptes++; 931 932 ret = 0; 933 out_unlock: 934 spin_unlock(&src_mm->page_table_lock); 935 spin_unlock(&dst_mm->page_table_lock); 936 out: 937 return ret; 938 } 939 940 void huge_pmd_set_accessed(struct mm_struct *mm, 941 struct vm_area_struct *vma, 942 unsigned long address, 943 pmd_t *pmd, pmd_t orig_pmd, 944 int dirty) 945 { 946 pmd_t entry; 947 unsigned long haddr; 948 949 spin_lock(&mm->page_table_lock); 950 if (unlikely(!pmd_same(*pmd, orig_pmd))) 951 goto unlock; 952 953 entry = pmd_mkyoung(orig_pmd); 954 haddr = address & HPAGE_PMD_MASK; 955 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty)) 956 update_mmu_cache_pmd(vma, address, pmd); 957 958 unlock: 959 spin_unlock(&mm->page_table_lock); 960 } 961 962 static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, 963 struct vm_area_struct *vma, unsigned long address, 964 pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr) 965 { 966 pgtable_t pgtable; 967 pmd_t _pmd; 968 struct page *page; 969 int i, ret = 0; 970 unsigned long mmun_start; /* For mmu_notifiers */ 971 unsigned long mmun_end; /* For mmu_notifiers */ 972 973 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); 974 if (!page) { 975 ret |= VM_FAULT_OOM; 976 goto out; 977 } 978 979 if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) { 980 put_page(page); 981 ret |= VM_FAULT_OOM; 982 goto out; 983 } 984 985 clear_user_highpage(page, address); 986 __SetPageUptodate(page); 987 988 mmun_start = haddr; 989 mmun_end = haddr + HPAGE_PMD_SIZE; 990 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 991 992 spin_lock(&mm->page_table_lock); 993 if (unlikely(!pmd_same(*pmd, orig_pmd))) 994 goto out_free_page; 995 996 pmdp_clear_flush(vma, haddr, pmd); 997 /* leave pmd empty until pte is filled */ 998 999 pgtable = pgtable_trans_huge_withdraw(mm); 1000 pmd_populate(mm, &_pmd, pgtable); 1001 1002 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1003 pte_t *pte, entry; 1004 if (haddr == (address & PAGE_MASK)) { 1005 entry = mk_pte(page, vma->vm_page_prot); 1006 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1007 page_add_new_anon_rmap(page, vma, haddr); 1008 } else { 1009 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 1010 entry = pte_mkspecial(entry); 1011 } 1012 pte = pte_offset_map(&_pmd, haddr); 1013 VM_BUG_ON(!pte_none(*pte)); 1014 set_pte_at(mm, haddr, pte, entry); 1015 pte_unmap(pte); 1016 } 1017 smp_wmb(); /* make pte visible before pmd */ 1018 pmd_populate(mm, pmd, pgtable); 1019 spin_unlock(&mm->page_table_lock); 1020 put_huge_zero_page(); 1021 inc_mm_counter(mm, MM_ANONPAGES); 1022 1023 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1024 1025 ret |= VM_FAULT_WRITE; 1026 out: 1027 return ret; 1028 out_free_page: 1029 spin_unlock(&mm->page_table_lock); 1030 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1031 mem_cgroup_uncharge_page(page); 1032 put_page(page); 1033 goto out; 1034 } 1035 1036 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 1037 struct vm_area_struct *vma, 1038 unsigned long address, 1039 pmd_t *pmd, pmd_t orig_pmd, 1040 struct page *page, 1041 unsigned long haddr) 1042 { 1043 pgtable_t pgtable; 1044 pmd_t _pmd; 1045 int ret = 0, i; 1046 struct page **pages; 1047 unsigned long mmun_start; /* For mmu_notifiers */ 1048 unsigned long mmun_end; /* For mmu_notifiers */ 1049 1050 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 1051 GFP_KERNEL); 1052 if (unlikely(!pages)) { 1053 ret |= VM_FAULT_OOM; 1054 goto out; 1055 } 1056 1057 for (i = 0; i < HPAGE_PMD_NR; i++) { 1058 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 1059 __GFP_OTHER_NODE, 1060 vma, address, page_to_nid(page)); 1061 if (unlikely(!pages[i] || 1062 mem_cgroup_newpage_charge(pages[i], mm, 1063 GFP_KERNEL))) { 1064 if (pages[i]) 1065 put_page(pages[i]); 1066 mem_cgroup_uncharge_start(); 1067 while (--i >= 0) { 1068 mem_cgroup_uncharge_page(pages[i]); 1069 put_page(pages[i]); 1070 } 1071 mem_cgroup_uncharge_end(); 1072 kfree(pages); 1073 ret |= VM_FAULT_OOM; 1074 goto out; 1075 } 1076 } 1077 1078 for (i = 0; i < HPAGE_PMD_NR; i++) { 1079 copy_user_highpage(pages[i], page + i, 1080 haddr + PAGE_SIZE * i, vma); 1081 __SetPageUptodate(pages[i]); 1082 cond_resched(); 1083 } 1084 1085 mmun_start = haddr; 1086 mmun_end = haddr + HPAGE_PMD_SIZE; 1087 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1088 1089 spin_lock(&mm->page_table_lock); 1090 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1091 goto out_free_pages; 1092 VM_BUG_ON(!PageHead(page)); 1093 1094 pmdp_clear_flush(vma, haddr, pmd); 1095 /* leave pmd empty until pte is filled */ 1096 1097 pgtable = pgtable_trans_huge_withdraw(mm); 1098 pmd_populate(mm, &_pmd, pgtable); 1099 1100 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1101 pte_t *pte, entry; 1102 entry = mk_pte(pages[i], vma->vm_page_prot); 1103 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1104 page_add_new_anon_rmap(pages[i], vma, haddr); 1105 pte = pte_offset_map(&_pmd, haddr); 1106 VM_BUG_ON(!pte_none(*pte)); 1107 set_pte_at(mm, haddr, pte, entry); 1108 pte_unmap(pte); 1109 } 1110 kfree(pages); 1111 1112 smp_wmb(); /* make pte visible before pmd */ 1113 pmd_populate(mm, pmd, pgtable); 1114 page_remove_rmap(page); 1115 spin_unlock(&mm->page_table_lock); 1116 1117 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1118 1119 ret |= VM_FAULT_WRITE; 1120 put_page(page); 1121 1122 out: 1123 return ret; 1124 1125 out_free_pages: 1126 spin_unlock(&mm->page_table_lock); 1127 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1128 mem_cgroup_uncharge_start(); 1129 for (i = 0; i < HPAGE_PMD_NR; i++) { 1130 mem_cgroup_uncharge_page(pages[i]); 1131 put_page(pages[i]); 1132 } 1133 mem_cgroup_uncharge_end(); 1134 kfree(pages); 1135 goto out; 1136 } 1137 1138 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 1139 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 1140 { 1141 int ret = 0; 1142 struct page *page = NULL, *new_page; 1143 unsigned long haddr; 1144 unsigned long mmun_start; /* For mmu_notifiers */ 1145 unsigned long mmun_end; /* For mmu_notifiers */ 1146 1147 VM_BUG_ON(!vma->anon_vma); 1148 haddr = address & HPAGE_PMD_MASK; 1149 if (is_huge_zero_pmd(orig_pmd)) 1150 goto alloc; 1151 spin_lock(&mm->page_table_lock); 1152 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1153 goto out_unlock; 1154 1155 page = pmd_page(orig_pmd); 1156 VM_BUG_ON(!PageCompound(page) || !PageHead(page)); 1157 if (page_mapcount(page) == 1) { 1158 pmd_t entry; 1159 entry = pmd_mkyoung(orig_pmd); 1160 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1161 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 1162 update_mmu_cache_pmd(vma, address, pmd); 1163 ret |= VM_FAULT_WRITE; 1164 goto out_unlock; 1165 } 1166 get_page(page); 1167 spin_unlock(&mm->page_table_lock); 1168 alloc: 1169 if (transparent_hugepage_enabled(vma) && 1170 !transparent_hugepage_debug_cow()) 1171 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 1172 vma, haddr, numa_node_id(), 0); 1173 else 1174 new_page = NULL; 1175 1176 if (unlikely(!new_page)) { 1177 count_vm_event(THP_FAULT_FALLBACK); 1178 if (is_huge_zero_pmd(orig_pmd)) { 1179 ret = do_huge_pmd_wp_zero_page_fallback(mm, vma, 1180 address, pmd, orig_pmd, haddr); 1181 } else { 1182 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 1183 pmd, orig_pmd, page, haddr); 1184 if (ret & VM_FAULT_OOM) 1185 split_huge_page(page); 1186 put_page(page); 1187 } 1188 goto out; 1189 } 1190 count_vm_event(THP_FAULT_ALLOC); 1191 1192 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 1193 put_page(new_page); 1194 if (page) { 1195 split_huge_page(page); 1196 put_page(page); 1197 } 1198 ret |= VM_FAULT_OOM; 1199 goto out; 1200 } 1201 1202 if (is_huge_zero_pmd(orig_pmd)) 1203 clear_huge_page(new_page, haddr, HPAGE_PMD_NR); 1204 else 1205 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 1206 __SetPageUptodate(new_page); 1207 1208 mmun_start = haddr; 1209 mmun_end = haddr + HPAGE_PMD_SIZE; 1210 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1211 1212 spin_lock(&mm->page_table_lock); 1213 if (page) 1214 put_page(page); 1215 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 1216 spin_unlock(&mm->page_table_lock); 1217 mem_cgroup_uncharge_page(new_page); 1218 put_page(new_page); 1219 goto out_mn; 1220 } else { 1221 pmd_t entry; 1222 entry = mk_huge_pmd(new_page, vma); 1223 pmdp_clear_flush(vma, haddr, pmd); 1224 page_add_new_anon_rmap(new_page, vma, haddr); 1225 set_pmd_at(mm, haddr, pmd, entry); 1226 update_mmu_cache_pmd(vma, address, pmd); 1227 if (is_huge_zero_pmd(orig_pmd)) { 1228 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 1229 put_huge_zero_page(); 1230 } else { 1231 VM_BUG_ON(!PageHead(page)); 1232 page_remove_rmap(page); 1233 put_page(page); 1234 } 1235 ret |= VM_FAULT_WRITE; 1236 } 1237 spin_unlock(&mm->page_table_lock); 1238 out_mn: 1239 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1240 out: 1241 return ret; 1242 out_unlock: 1243 spin_unlock(&mm->page_table_lock); 1244 return ret; 1245 } 1246 1247 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1248 unsigned long addr, 1249 pmd_t *pmd, 1250 unsigned int flags) 1251 { 1252 struct mm_struct *mm = vma->vm_mm; 1253 struct page *page = NULL; 1254 1255 assert_spin_locked(&mm->page_table_lock); 1256 1257 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1258 goto out; 1259 1260 page = pmd_page(*pmd); 1261 VM_BUG_ON(!PageHead(page)); 1262 if (flags & FOLL_TOUCH) { 1263 pmd_t _pmd; 1264 /* 1265 * We should set the dirty bit only for FOLL_WRITE but 1266 * for now the dirty bit in the pmd is meaningless. 1267 * And if the dirty bit will become meaningful and 1268 * we'll only set it with FOLL_WRITE, an atomic 1269 * set_bit will be required on the pmd to set the 1270 * young bit, instead of the current set_pmd_at. 1271 */ 1272 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 1273 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd); 1274 } 1275 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1276 if (page->mapping && trylock_page(page)) { 1277 lru_add_drain(); 1278 if (page->mapping) 1279 mlock_vma_page(page); 1280 unlock_page(page); 1281 } 1282 } 1283 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1284 VM_BUG_ON(!PageCompound(page)); 1285 if (flags & FOLL_GET) 1286 get_page_foll(page); 1287 1288 out: 1289 return page; 1290 } 1291 1292 /* NUMA hinting page fault entry point for trans huge pmds */ 1293 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, 1294 unsigned long addr, pmd_t pmd, pmd_t *pmdp) 1295 { 1296 struct page *page; 1297 unsigned long haddr = addr & HPAGE_PMD_MASK; 1298 int target_nid; 1299 int current_nid = -1; 1300 bool migrated; 1301 bool page_locked = false; 1302 1303 spin_lock(&mm->page_table_lock); 1304 if (unlikely(!pmd_same(pmd, *pmdp))) 1305 goto out_unlock; 1306 1307 page = pmd_page(pmd); 1308 get_page(page); 1309 current_nid = page_to_nid(page); 1310 count_vm_numa_event(NUMA_HINT_FAULTS); 1311 if (current_nid == numa_node_id()) 1312 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1313 1314 target_nid = mpol_misplaced(page, vma, haddr); 1315 if (target_nid == -1) { 1316 put_page(page); 1317 goto clear_pmdnuma; 1318 } 1319 1320 /* Acquire the page lock to serialise THP migrations */ 1321 spin_unlock(&mm->page_table_lock); 1322 lock_page(page); 1323 page_locked = true; 1324 1325 /* Confirm the PTE did not while locked */ 1326 spin_lock(&mm->page_table_lock); 1327 if (unlikely(!pmd_same(pmd, *pmdp))) { 1328 unlock_page(page); 1329 put_page(page); 1330 goto out_unlock; 1331 } 1332 spin_unlock(&mm->page_table_lock); 1333 1334 /* Migrate the THP to the requested node */ 1335 migrated = migrate_misplaced_transhuge_page(mm, vma, 1336 pmdp, pmd, addr, 1337 page, target_nid); 1338 if (migrated) 1339 current_nid = target_nid; 1340 else { 1341 spin_lock(&mm->page_table_lock); 1342 if (unlikely(!pmd_same(pmd, *pmdp))) { 1343 unlock_page(page); 1344 goto out_unlock; 1345 } 1346 goto clear_pmdnuma; 1347 } 1348 1349 task_numa_fault(current_nid, HPAGE_PMD_NR, migrated); 1350 return 0; 1351 1352 clear_pmdnuma: 1353 pmd = pmd_mknonnuma(pmd); 1354 set_pmd_at(mm, haddr, pmdp, pmd); 1355 VM_BUG_ON(pmd_numa(*pmdp)); 1356 update_mmu_cache_pmd(vma, addr, pmdp); 1357 if (page_locked) 1358 unlock_page(page); 1359 1360 out_unlock: 1361 spin_unlock(&mm->page_table_lock); 1362 if (current_nid != -1) 1363 task_numa_fault(current_nid, HPAGE_PMD_NR, migrated); 1364 return 0; 1365 } 1366 1367 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1368 pmd_t *pmd, unsigned long addr) 1369 { 1370 int ret = 0; 1371 1372 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1373 struct page *page; 1374 pgtable_t pgtable; 1375 pmd_t orig_pmd; 1376 pgtable = pgtable_trans_huge_withdraw(tlb->mm); 1377 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd); 1378 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1379 if (is_huge_zero_pmd(orig_pmd)) { 1380 tlb->mm->nr_ptes--; 1381 spin_unlock(&tlb->mm->page_table_lock); 1382 put_huge_zero_page(); 1383 } else { 1384 page = pmd_page(orig_pmd); 1385 page_remove_rmap(page); 1386 VM_BUG_ON(page_mapcount(page) < 0); 1387 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1388 VM_BUG_ON(!PageHead(page)); 1389 tlb->mm->nr_ptes--; 1390 spin_unlock(&tlb->mm->page_table_lock); 1391 tlb_remove_page(tlb, page); 1392 } 1393 pte_free(tlb->mm, pgtable); 1394 ret = 1; 1395 } 1396 return ret; 1397 } 1398 1399 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1400 unsigned long addr, unsigned long end, 1401 unsigned char *vec) 1402 { 1403 int ret = 0; 1404 1405 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1406 /* 1407 * All logical pages in the range are present 1408 * if backed by a huge page. 1409 */ 1410 spin_unlock(&vma->vm_mm->page_table_lock); 1411 memset(vec, 1, (end - addr) >> PAGE_SHIFT); 1412 ret = 1; 1413 } 1414 1415 return ret; 1416 } 1417 1418 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, 1419 unsigned long old_addr, 1420 unsigned long new_addr, unsigned long old_end, 1421 pmd_t *old_pmd, pmd_t *new_pmd) 1422 { 1423 int ret = 0; 1424 pmd_t pmd; 1425 1426 struct mm_struct *mm = vma->vm_mm; 1427 1428 if ((old_addr & ~HPAGE_PMD_MASK) || 1429 (new_addr & ~HPAGE_PMD_MASK) || 1430 old_end - old_addr < HPAGE_PMD_SIZE || 1431 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1432 goto out; 1433 1434 /* 1435 * The destination pmd shouldn't be established, free_pgtables() 1436 * should have release it. 1437 */ 1438 if (WARN_ON(!pmd_none(*new_pmd))) { 1439 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1440 goto out; 1441 } 1442 1443 ret = __pmd_trans_huge_lock(old_pmd, vma); 1444 if (ret == 1) { 1445 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); 1446 VM_BUG_ON(!pmd_none(*new_pmd)); 1447 set_pmd_at(mm, new_addr, new_pmd, pmd); 1448 spin_unlock(&mm->page_table_lock); 1449 } 1450 out: 1451 return ret; 1452 } 1453 1454 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1455 unsigned long addr, pgprot_t newprot, int prot_numa) 1456 { 1457 struct mm_struct *mm = vma->vm_mm; 1458 int ret = 0; 1459 1460 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1461 pmd_t entry; 1462 entry = pmdp_get_and_clear(mm, addr, pmd); 1463 if (!prot_numa) { 1464 entry = pmd_modify(entry, newprot); 1465 BUG_ON(pmd_write(entry)); 1466 } else { 1467 struct page *page = pmd_page(*pmd); 1468 1469 /* only check non-shared pages */ 1470 if (page_mapcount(page) == 1 && 1471 !pmd_numa(*pmd)) { 1472 entry = pmd_mknuma(entry); 1473 } 1474 } 1475 set_pmd_at(mm, addr, pmd, entry); 1476 spin_unlock(&vma->vm_mm->page_table_lock); 1477 ret = 1; 1478 } 1479 1480 return ret; 1481 } 1482 1483 /* 1484 * Returns 1 if a given pmd maps a stable (not under splitting) thp. 1485 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. 1486 * 1487 * Note that if it returns 1, this routine returns without unlocking page 1488 * table locks. So callers must unlock them. 1489 */ 1490 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 1491 { 1492 spin_lock(&vma->vm_mm->page_table_lock); 1493 if (likely(pmd_trans_huge(*pmd))) { 1494 if (unlikely(pmd_trans_splitting(*pmd))) { 1495 spin_unlock(&vma->vm_mm->page_table_lock); 1496 wait_split_huge_page(vma->anon_vma, pmd); 1497 return -1; 1498 } else { 1499 /* Thp mapped by 'pmd' is stable, so we can 1500 * handle it as it is. */ 1501 return 1; 1502 } 1503 } 1504 spin_unlock(&vma->vm_mm->page_table_lock); 1505 return 0; 1506 } 1507 1508 pmd_t *page_check_address_pmd(struct page *page, 1509 struct mm_struct *mm, 1510 unsigned long address, 1511 enum page_check_address_pmd_flag flag) 1512 { 1513 pmd_t *pmd, *ret = NULL; 1514 1515 if (address & ~HPAGE_PMD_MASK) 1516 goto out; 1517 1518 pmd = mm_find_pmd(mm, address); 1519 if (!pmd) 1520 goto out; 1521 if (pmd_none(*pmd)) 1522 goto out; 1523 if (pmd_page(*pmd) != page) 1524 goto out; 1525 /* 1526 * split_vma() may create temporary aliased mappings. There is 1527 * no risk as long as all huge pmd are found and have their 1528 * splitting bit set before __split_huge_page_refcount 1529 * runs. Finding the same huge pmd more than once during the 1530 * same rmap walk is not a problem. 1531 */ 1532 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1533 pmd_trans_splitting(*pmd)) 1534 goto out; 1535 if (pmd_trans_huge(*pmd)) { 1536 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1537 !pmd_trans_splitting(*pmd)); 1538 ret = pmd; 1539 } 1540 out: 1541 return ret; 1542 } 1543 1544 static int __split_huge_page_splitting(struct page *page, 1545 struct vm_area_struct *vma, 1546 unsigned long address) 1547 { 1548 struct mm_struct *mm = vma->vm_mm; 1549 pmd_t *pmd; 1550 int ret = 0; 1551 /* For mmu_notifiers */ 1552 const unsigned long mmun_start = address; 1553 const unsigned long mmun_end = address + HPAGE_PMD_SIZE; 1554 1555 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1556 spin_lock(&mm->page_table_lock); 1557 pmd = page_check_address_pmd(page, mm, address, 1558 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); 1559 if (pmd) { 1560 /* 1561 * We can't temporarily set the pmd to null in order 1562 * to split it, the pmd must remain marked huge at all 1563 * times or the VM won't take the pmd_trans_huge paths 1564 * and it won't wait on the anon_vma->root->rwsem to 1565 * serialize against split_huge_page*. 1566 */ 1567 pmdp_splitting_flush(vma, address, pmd); 1568 ret = 1; 1569 } 1570 spin_unlock(&mm->page_table_lock); 1571 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1572 1573 return ret; 1574 } 1575 1576 static void __split_huge_page_refcount(struct page *page) 1577 { 1578 int i; 1579 struct zone *zone = page_zone(page); 1580 struct lruvec *lruvec; 1581 int tail_count = 0; 1582 1583 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1584 spin_lock_irq(&zone->lru_lock); 1585 lruvec = mem_cgroup_page_lruvec(page, zone); 1586 1587 compound_lock(page); 1588 /* complete memcg works before add pages to LRU */ 1589 mem_cgroup_split_huge_fixup(page); 1590 1591 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 1592 struct page *page_tail = page + i; 1593 1594 /* tail_page->_mapcount cannot change */ 1595 BUG_ON(page_mapcount(page_tail) < 0); 1596 tail_count += page_mapcount(page_tail); 1597 /* check for overflow */ 1598 BUG_ON(tail_count < 0); 1599 BUG_ON(atomic_read(&page_tail->_count) != 0); 1600 /* 1601 * tail_page->_count is zero and not changing from 1602 * under us. But get_page_unless_zero() may be running 1603 * from under us on the tail_page. If we used 1604 * atomic_set() below instead of atomic_add(), we 1605 * would then run atomic_set() concurrently with 1606 * get_page_unless_zero(), and atomic_set() is 1607 * implemented in C not using locked ops. spin_unlock 1608 * on x86 sometime uses locked ops because of PPro 1609 * errata 66, 92, so unless somebody can guarantee 1610 * atomic_set() here would be safe on all archs (and 1611 * not only on x86), it's safer to use atomic_add(). 1612 */ 1613 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1614 &page_tail->_count); 1615 1616 /* after clearing PageTail the gup refcount can be released */ 1617 smp_mb(); 1618 1619 /* 1620 * retain hwpoison flag of the poisoned tail page: 1621 * fix for the unsuitable process killed on Guest Machine(KVM) 1622 * by the memory-failure. 1623 */ 1624 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1625 page_tail->flags |= (page->flags & 1626 ((1L << PG_referenced) | 1627 (1L << PG_swapbacked) | 1628 (1L << PG_mlocked) | 1629 (1L << PG_uptodate))); 1630 page_tail->flags |= (1L << PG_dirty); 1631 1632 /* clear PageTail before overwriting first_page */ 1633 smp_wmb(); 1634 1635 /* 1636 * __split_huge_page_splitting() already set the 1637 * splitting bit in all pmd that could map this 1638 * hugepage, that will ensure no CPU can alter the 1639 * mapcount on the head page. The mapcount is only 1640 * accounted in the head page and it has to be 1641 * transferred to all tail pages in the below code. So 1642 * for this code to be safe, the split the mapcount 1643 * can't change. But that doesn't mean userland can't 1644 * keep changing and reading the page contents while 1645 * we transfer the mapcount, so the pmd splitting 1646 * status is achieved setting a reserved bit in the 1647 * pmd, not by clearing the present bit. 1648 */ 1649 page_tail->_mapcount = page->_mapcount; 1650 1651 BUG_ON(page_tail->mapping); 1652 page_tail->mapping = page->mapping; 1653 1654 page_tail->index = page->index + i; 1655 page_xchg_last_nid(page_tail, page_last_nid(page)); 1656 1657 BUG_ON(!PageAnon(page_tail)); 1658 BUG_ON(!PageUptodate(page_tail)); 1659 BUG_ON(!PageDirty(page_tail)); 1660 BUG_ON(!PageSwapBacked(page_tail)); 1661 1662 lru_add_page_tail(page, page_tail, lruvec); 1663 } 1664 atomic_sub(tail_count, &page->_count); 1665 BUG_ON(atomic_read(&page->_count) <= 0); 1666 1667 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); 1668 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); 1669 1670 ClearPageCompound(page); 1671 compound_unlock(page); 1672 spin_unlock_irq(&zone->lru_lock); 1673 1674 for (i = 1; i < HPAGE_PMD_NR; i++) { 1675 struct page *page_tail = page + i; 1676 BUG_ON(page_count(page_tail) <= 0); 1677 /* 1678 * Tail pages may be freed if there wasn't any mapping 1679 * like if add_to_swap() is running on a lru page that 1680 * had its mapping zapped. And freeing these pages 1681 * requires taking the lru_lock so we do the put_page 1682 * of the tail pages after the split is complete. 1683 */ 1684 put_page(page_tail); 1685 } 1686 1687 /* 1688 * Only the head page (now become a regular page) is required 1689 * to be pinned by the caller. 1690 */ 1691 BUG_ON(page_count(page) <= 0); 1692 } 1693 1694 static int __split_huge_page_map(struct page *page, 1695 struct vm_area_struct *vma, 1696 unsigned long address) 1697 { 1698 struct mm_struct *mm = vma->vm_mm; 1699 pmd_t *pmd, _pmd; 1700 int ret = 0, i; 1701 pgtable_t pgtable; 1702 unsigned long haddr; 1703 1704 spin_lock(&mm->page_table_lock); 1705 pmd = page_check_address_pmd(page, mm, address, 1706 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); 1707 if (pmd) { 1708 pgtable = pgtable_trans_huge_withdraw(mm); 1709 pmd_populate(mm, &_pmd, pgtable); 1710 1711 haddr = address; 1712 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1713 pte_t *pte, entry; 1714 BUG_ON(PageCompound(page+i)); 1715 entry = mk_pte(page + i, vma->vm_page_prot); 1716 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1717 if (!pmd_write(*pmd)) 1718 entry = pte_wrprotect(entry); 1719 else 1720 BUG_ON(page_mapcount(page) != 1); 1721 if (!pmd_young(*pmd)) 1722 entry = pte_mkold(entry); 1723 if (pmd_numa(*pmd)) 1724 entry = pte_mknuma(entry); 1725 pte = pte_offset_map(&_pmd, haddr); 1726 BUG_ON(!pte_none(*pte)); 1727 set_pte_at(mm, haddr, pte, entry); 1728 pte_unmap(pte); 1729 } 1730 1731 smp_wmb(); /* make pte visible before pmd */ 1732 /* 1733 * Up to this point the pmd is present and huge and 1734 * userland has the whole access to the hugepage 1735 * during the split (which happens in place). If we 1736 * overwrite the pmd with the not-huge version 1737 * pointing to the pte here (which of course we could 1738 * if all CPUs were bug free), userland could trigger 1739 * a small page size TLB miss on the small sized TLB 1740 * while the hugepage TLB entry is still established 1741 * in the huge TLB. Some CPU doesn't like that. See 1742 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1743 * Erratum 383 on page 93. Intel should be safe but is 1744 * also warns that it's only safe if the permission 1745 * and cache attributes of the two entries loaded in 1746 * the two TLB is identical (which should be the case 1747 * here). But it is generally safer to never allow 1748 * small and huge TLB entries for the same virtual 1749 * address to be loaded simultaneously. So instead of 1750 * doing "pmd_populate(); flush_tlb_range();" we first 1751 * mark the current pmd notpresent (atomically because 1752 * here the pmd_trans_huge and pmd_trans_splitting 1753 * must remain set at all times on the pmd until the 1754 * split is complete for this pmd), then we flush the 1755 * SMP TLB and finally we write the non-huge version 1756 * of the pmd entry with pmd_populate. 1757 */ 1758 pmdp_invalidate(vma, address, pmd); 1759 pmd_populate(mm, pmd, pgtable); 1760 ret = 1; 1761 } 1762 spin_unlock(&mm->page_table_lock); 1763 1764 return ret; 1765 } 1766 1767 /* must be called with anon_vma->root->rwsem held */ 1768 static void __split_huge_page(struct page *page, 1769 struct anon_vma *anon_vma) 1770 { 1771 int mapcount, mapcount2; 1772 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 1773 struct anon_vma_chain *avc; 1774 1775 BUG_ON(!PageHead(page)); 1776 BUG_ON(PageTail(page)); 1777 1778 mapcount = 0; 1779 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1780 struct vm_area_struct *vma = avc->vma; 1781 unsigned long addr = vma_address(page, vma); 1782 BUG_ON(is_vma_temporary_stack(vma)); 1783 mapcount += __split_huge_page_splitting(page, vma, addr); 1784 } 1785 /* 1786 * It is critical that new vmas are added to the tail of the 1787 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1788 * and establishes a child pmd before 1789 * __split_huge_page_splitting() freezes the parent pmd (so if 1790 * we fail to prevent copy_huge_pmd() from running until the 1791 * whole __split_huge_page() is complete), we will still see 1792 * the newly established pmd of the child later during the 1793 * walk, to be able to set it as pmd_trans_splitting too. 1794 */ 1795 if (mapcount != page_mapcount(page)) 1796 printk(KERN_ERR "mapcount %d page_mapcount %d\n", 1797 mapcount, page_mapcount(page)); 1798 BUG_ON(mapcount != page_mapcount(page)); 1799 1800 __split_huge_page_refcount(page); 1801 1802 mapcount2 = 0; 1803 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1804 struct vm_area_struct *vma = avc->vma; 1805 unsigned long addr = vma_address(page, vma); 1806 BUG_ON(is_vma_temporary_stack(vma)); 1807 mapcount2 += __split_huge_page_map(page, vma, addr); 1808 } 1809 if (mapcount != mapcount2) 1810 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", 1811 mapcount, mapcount2, page_mapcount(page)); 1812 BUG_ON(mapcount != mapcount2); 1813 } 1814 1815 int split_huge_page(struct page *page) 1816 { 1817 struct anon_vma *anon_vma; 1818 int ret = 1; 1819 1820 BUG_ON(is_huge_zero_pfn(page_to_pfn(page))); 1821 BUG_ON(!PageAnon(page)); 1822 1823 /* 1824 * The caller does not necessarily hold an mmap_sem that would prevent 1825 * the anon_vma disappearing so we first we take a reference to it 1826 * and then lock the anon_vma for write. This is similar to 1827 * page_lock_anon_vma_read except the write lock is taken to serialise 1828 * against parallel split or collapse operations. 1829 */ 1830 anon_vma = page_get_anon_vma(page); 1831 if (!anon_vma) 1832 goto out; 1833 anon_vma_lock_write(anon_vma); 1834 1835 ret = 0; 1836 if (!PageCompound(page)) 1837 goto out_unlock; 1838 1839 BUG_ON(!PageSwapBacked(page)); 1840 __split_huge_page(page, anon_vma); 1841 count_vm_event(THP_SPLIT); 1842 1843 BUG_ON(PageCompound(page)); 1844 out_unlock: 1845 anon_vma_unlock(anon_vma); 1846 put_anon_vma(anon_vma); 1847 out: 1848 return ret; 1849 } 1850 1851 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE) 1852 1853 int hugepage_madvise(struct vm_area_struct *vma, 1854 unsigned long *vm_flags, int advice) 1855 { 1856 struct mm_struct *mm = vma->vm_mm; 1857 1858 switch (advice) { 1859 case MADV_HUGEPAGE: 1860 /* 1861 * Be somewhat over-protective like KSM for now! 1862 */ 1863 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1864 return -EINVAL; 1865 if (mm->def_flags & VM_NOHUGEPAGE) 1866 return -EINVAL; 1867 *vm_flags &= ~VM_NOHUGEPAGE; 1868 *vm_flags |= VM_HUGEPAGE; 1869 /* 1870 * If the vma become good for khugepaged to scan, 1871 * register it here without waiting a page fault that 1872 * may not happen any time soon. 1873 */ 1874 if (unlikely(khugepaged_enter_vma_merge(vma))) 1875 return -ENOMEM; 1876 break; 1877 case MADV_NOHUGEPAGE: 1878 /* 1879 * Be somewhat over-protective like KSM for now! 1880 */ 1881 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1882 return -EINVAL; 1883 *vm_flags &= ~VM_HUGEPAGE; 1884 *vm_flags |= VM_NOHUGEPAGE; 1885 /* 1886 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1887 * this vma even if we leave the mm registered in khugepaged if 1888 * it got registered before VM_NOHUGEPAGE was set. 1889 */ 1890 break; 1891 } 1892 1893 return 0; 1894 } 1895 1896 static int __init khugepaged_slab_init(void) 1897 { 1898 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1899 sizeof(struct mm_slot), 1900 __alignof__(struct mm_slot), 0, NULL); 1901 if (!mm_slot_cache) 1902 return -ENOMEM; 1903 1904 return 0; 1905 } 1906 1907 static void __init khugepaged_slab_free(void) 1908 { 1909 kmem_cache_destroy(mm_slot_cache); 1910 mm_slot_cache = NULL; 1911 } 1912 1913 static inline struct mm_slot *alloc_mm_slot(void) 1914 { 1915 if (!mm_slot_cache) /* initialization failed */ 1916 return NULL; 1917 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1918 } 1919 1920 static inline void free_mm_slot(struct mm_slot *mm_slot) 1921 { 1922 kmem_cache_free(mm_slot_cache, mm_slot); 1923 } 1924 1925 static int __init mm_slots_hash_init(void) 1926 { 1927 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), 1928 GFP_KERNEL); 1929 if (!mm_slots_hash) 1930 return -ENOMEM; 1931 return 0; 1932 } 1933 1934 #if 0 1935 static void __init mm_slots_hash_free(void) 1936 { 1937 kfree(mm_slots_hash); 1938 mm_slots_hash = NULL; 1939 } 1940 #endif 1941 1942 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1943 { 1944 struct mm_slot *mm_slot; 1945 struct hlist_head *bucket; 1946 struct hlist_node *node; 1947 1948 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1949 % MM_SLOTS_HASH_HEADS]; 1950 hlist_for_each_entry(mm_slot, node, bucket, hash) { 1951 if (mm == mm_slot->mm) 1952 return mm_slot; 1953 } 1954 return NULL; 1955 } 1956 1957 static void insert_to_mm_slots_hash(struct mm_struct *mm, 1958 struct mm_slot *mm_slot) 1959 { 1960 struct hlist_head *bucket; 1961 1962 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1963 % MM_SLOTS_HASH_HEADS]; 1964 mm_slot->mm = mm; 1965 hlist_add_head(&mm_slot->hash, bucket); 1966 } 1967 1968 static inline int khugepaged_test_exit(struct mm_struct *mm) 1969 { 1970 return atomic_read(&mm->mm_users) == 0; 1971 } 1972 1973 int __khugepaged_enter(struct mm_struct *mm) 1974 { 1975 struct mm_slot *mm_slot; 1976 int wakeup; 1977 1978 mm_slot = alloc_mm_slot(); 1979 if (!mm_slot) 1980 return -ENOMEM; 1981 1982 /* __khugepaged_exit() must not run from under us */ 1983 VM_BUG_ON(khugepaged_test_exit(mm)); 1984 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1985 free_mm_slot(mm_slot); 1986 return 0; 1987 } 1988 1989 spin_lock(&khugepaged_mm_lock); 1990 insert_to_mm_slots_hash(mm, mm_slot); 1991 /* 1992 * Insert just behind the scanning cursor, to let the area settle 1993 * down a little. 1994 */ 1995 wakeup = list_empty(&khugepaged_scan.mm_head); 1996 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1997 spin_unlock(&khugepaged_mm_lock); 1998 1999 atomic_inc(&mm->mm_count); 2000 if (wakeup) 2001 wake_up_interruptible(&khugepaged_wait); 2002 2003 return 0; 2004 } 2005 2006 int khugepaged_enter_vma_merge(struct vm_area_struct *vma) 2007 { 2008 unsigned long hstart, hend; 2009 if (!vma->anon_vma) 2010 /* 2011 * Not yet faulted in so we will register later in the 2012 * page fault if needed. 2013 */ 2014 return 0; 2015 if (vma->vm_ops) 2016 /* khugepaged not yet working on file or special mappings */ 2017 return 0; 2018 VM_BUG_ON(vma->vm_flags & VM_NO_THP); 2019 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2020 hend = vma->vm_end & HPAGE_PMD_MASK; 2021 if (hstart < hend) 2022 return khugepaged_enter(vma); 2023 return 0; 2024 } 2025 2026 void __khugepaged_exit(struct mm_struct *mm) 2027 { 2028 struct mm_slot *mm_slot; 2029 int free = 0; 2030 2031 spin_lock(&khugepaged_mm_lock); 2032 mm_slot = get_mm_slot(mm); 2033 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 2034 hlist_del(&mm_slot->hash); 2035 list_del(&mm_slot->mm_node); 2036 free = 1; 2037 } 2038 spin_unlock(&khugepaged_mm_lock); 2039 2040 if (free) { 2041 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2042 free_mm_slot(mm_slot); 2043 mmdrop(mm); 2044 } else if (mm_slot) { 2045 /* 2046 * This is required to serialize against 2047 * khugepaged_test_exit() (which is guaranteed to run 2048 * under mmap sem read mode). Stop here (after we 2049 * return all pagetables will be destroyed) until 2050 * khugepaged has finished working on the pagetables 2051 * under the mmap_sem. 2052 */ 2053 down_write(&mm->mmap_sem); 2054 up_write(&mm->mmap_sem); 2055 } 2056 } 2057 2058 static void release_pte_page(struct page *page) 2059 { 2060 /* 0 stands for page_is_file_cache(page) == false */ 2061 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 2062 unlock_page(page); 2063 putback_lru_page(page); 2064 } 2065 2066 static void release_pte_pages(pte_t *pte, pte_t *_pte) 2067 { 2068 while (--_pte >= pte) { 2069 pte_t pteval = *_pte; 2070 if (!pte_none(pteval)) 2071 release_pte_page(pte_page(pteval)); 2072 } 2073 } 2074 2075 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 2076 unsigned long address, 2077 pte_t *pte) 2078 { 2079 struct page *page; 2080 pte_t *_pte; 2081 int referenced = 0, none = 0; 2082 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 2083 _pte++, address += PAGE_SIZE) { 2084 pte_t pteval = *_pte; 2085 if (pte_none(pteval)) { 2086 if (++none <= khugepaged_max_ptes_none) 2087 continue; 2088 else 2089 goto out; 2090 } 2091 if (!pte_present(pteval) || !pte_write(pteval)) 2092 goto out; 2093 page = vm_normal_page(vma, address, pteval); 2094 if (unlikely(!page)) 2095 goto out; 2096 2097 VM_BUG_ON(PageCompound(page)); 2098 BUG_ON(!PageAnon(page)); 2099 VM_BUG_ON(!PageSwapBacked(page)); 2100 2101 /* cannot use mapcount: can't collapse if there's a gup pin */ 2102 if (page_count(page) != 1) 2103 goto out; 2104 /* 2105 * We can do it before isolate_lru_page because the 2106 * page can't be freed from under us. NOTE: PG_lock 2107 * is needed to serialize against split_huge_page 2108 * when invoked from the VM. 2109 */ 2110 if (!trylock_page(page)) 2111 goto out; 2112 /* 2113 * Isolate the page to avoid collapsing an hugepage 2114 * currently in use by the VM. 2115 */ 2116 if (isolate_lru_page(page)) { 2117 unlock_page(page); 2118 goto out; 2119 } 2120 /* 0 stands for page_is_file_cache(page) == false */ 2121 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 2122 VM_BUG_ON(!PageLocked(page)); 2123 VM_BUG_ON(PageLRU(page)); 2124 2125 /* If there is no mapped pte young don't collapse the page */ 2126 if (pte_young(pteval) || PageReferenced(page) || 2127 mmu_notifier_test_young(vma->vm_mm, address)) 2128 referenced = 1; 2129 } 2130 if (likely(referenced)) 2131 return 1; 2132 out: 2133 release_pte_pages(pte, _pte); 2134 return 0; 2135 } 2136 2137 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 2138 struct vm_area_struct *vma, 2139 unsigned long address, 2140 spinlock_t *ptl) 2141 { 2142 pte_t *_pte; 2143 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 2144 pte_t pteval = *_pte; 2145 struct page *src_page; 2146 2147 if (pte_none(pteval)) { 2148 clear_user_highpage(page, address); 2149 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 2150 } else { 2151 src_page = pte_page(pteval); 2152 copy_user_highpage(page, src_page, address, vma); 2153 VM_BUG_ON(page_mapcount(src_page) != 1); 2154 release_pte_page(src_page); 2155 /* 2156 * ptl mostly unnecessary, but preempt has to 2157 * be disabled to update the per-cpu stats 2158 * inside page_remove_rmap(). 2159 */ 2160 spin_lock(ptl); 2161 /* 2162 * paravirt calls inside pte_clear here are 2163 * superfluous. 2164 */ 2165 pte_clear(vma->vm_mm, address, _pte); 2166 page_remove_rmap(src_page); 2167 spin_unlock(ptl); 2168 free_page_and_swap_cache(src_page); 2169 } 2170 2171 address += PAGE_SIZE; 2172 page++; 2173 } 2174 } 2175 2176 static void khugepaged_alloc_sleep(void) 2177 { 2178 wait_event_freezable_timeout(khugepaged_wait, false, 2179 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2180 } 2181 2182 #ifdef CONFIG_NUMA 2183 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2184 { 2185 if (IS_ERR(*hpage)) { 2186 if (!*wait) 2187 return false; 2188 2189 *wait = false; 2190 *hpage = NULL; 2191 khugepaged_alloc_sleep(); 2192 } else if (*hpage) { 2193 put_page(*hpage); 2194 *hpage = NULL; 2195 } 2196 2197 return true; 2198 } 2199 2200 static struct page 2201 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2202 struct vm_area_struct *vma, unsigned long address, 2203 int node) 2204 { 2205 VM_BUG_ON(*hpage); 2206 /* 2207 * Allocate the page while the vma is still valid and under 2208 * the mmap_sem read mode so there is no memory allocation 2209 * later when we take the mmap_sem in write mode. This is more 2210 * friendly behavior (OTOH it may actually hide bugs) to 2211 * filesystems in userland with daemons allocating memory in 2212 * the userland I/O paths. Allocating memory with the 2213 * mmap_sem in read mode is good idea also to allow greater 2214 * scalability. 2215 */ 2216 *hpage = alloc_hugepage_vma(khugepaged_defrag(), vma, address, 2217 node, __GFP_OTHER_NODE); 2218 2219 /* 2220 * After allocating the hugepage, release the mmap_sem read lock in 2221 * preparation for taking it in write mode. 2222 */ 2223 up_read(&mm->mmap_sem); 2224 if (unlikely(!*hpage)) { 2225 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2226 *hpage = ERR_PTR(-ENOMEM); 2227 return NULL; 2228 } 2229 2230 count_vm_event(THP_COLLAPSE_ALLOC); 2231 return *hpage; 2232 } 2233 #else 2234 static struct page *khugepaged_alloc_hugepage(bool *wait) 2235 { 2236 struct page *hpage; 2237 2238 do { 2239 hpage = alloc_hugepage(khugepaged_defrag()); 2240 if (!hpage) { 2241 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2242 if (!*wait) 2243 return NULL; 2244 2245 *wait = false; 2246 khugepaged_alloc_sleep(); 2247 } else 2248 count_vm_event(THP_COLLAPSE_ALLOC); 2249 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 2250 2251 return hpage; 2252 } 2253 2254 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2255 { 2256 if (!*hpage) 2257 *hpage = khugepaged_alloc_hugepage(wait); 2258 2259 if (unlikely(!*hpage)) 2260 return false; 2261 2262 return true; 2263 } 2264 2265 static struct page 2266 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2267 struct vm_area_struct *vma, unsigned long address, 2268 int node) 2269 { 2270 up_read(&mm->mmap_sem); 2271 VM_BUG_ON(!*hpage); 2272 return *hpage; 2273 } 2274 #endif 2275 2276 static bool hugepage_vma_check(struct vm_area_struct *vma) 2277 { 2278 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 2279 (vma->vm_flags & VM_NOHUGEPAGE)) 2280 return false; 2281 2282 if (!vma->anon_vma || vma->vm_ops) 2283 return false; 2284 if (is_vma_temporary_stack(vma)) 2285 return false; 2286 VM_BUG_ON(vma->vm_flags & VM_NO_THP); 2287 return true; 2288 } 2289 2290 static void collapse_huge_page(struct mm_struct *mm, 2291 unsigned long address, 2292 struct page **hpage, 2293 struct vm_area_struct *vma, 2294 int node) 2295 { 2296 pmd_t *pmd, _pmd; 2297 pte_t *pte; 2298 pgtable_t pgtable; 2299 struct page *new_page; 2300 spinlock_t *ptl; 2301 int isolated; 2302 unsigned long hstart, hend; 2303 unsigned long mmun_start; /* For mmu_notifiers */ 2304 unsigned long mmun_end; /* For mmu_notifiers */ 2305 2306 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2307 2308 /* release the mmap_sem read lock. */ 2309 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node); 2310 if (!new_page) 2311 return; 2312 2313 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) 2314 return; 2315 2316 /* 2317 * Prevent all access to pagetables with the exception of 2318 * gup_fast later hanlded by the ptep_clear_flush and the VM 2319 * handled by the anon_vma lock + PG_lock. 2320 */ 2321 down_write(&mm->mmap_sem); 2322 if (unlikely(khugepaged_test_exit(mm))) 2323 goto out; 2324 2325 vma = find_vma(mm, address); 2326 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2327 hend = vma->vm_end & HPAGE_PMD_MASK; 2328 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 2329 goto out; 2330 if (!hugepage_vma_check(vma)) 2331 goto out; 2332 pmd = mm_find_pmd(mm, address); 2333 if (!pmd) 2334 goto out; 2335 if (pmd_trans_huge(*pmd)) 2336 goto out; 2337 2338 anon_vma_lock_write(vma->anon_vma); 2339 2340 pte = pte_offset_map(pmd, address); 2341 ptl = pte_lockptr(mm, pmd); 2342 2343 mmun_start = address; 2344 mmun_end = address + HPAGE_PMD_SIZE; 2345 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2346 spin_lock(&mm->page_table_lock); /* probably unnecessary */ 2347 /* 2348 * After this gup_fast can't run anymore. This also removes 2349 * any huge TLB entry from the CPU so we won't allow 2350 * huge and small TLB entries for the same virtual address 2351 * to avoid the risk of CPU bugs in that area. 2352 */ 2353 _pmd = pmdp_clear_flush(vma, address, pmd); 2354 spin_unlock(&mm->page_table_lock); 2355 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2356 2357 spin_lock(ptl); 2358 isolated = __collapse_huge_page_isolate(vma, address, pte); 2359 spin_unlock(ptl); 2360 2361 if (unlikely(!isolated)) { 2362 pte_unmap(pte); 2363 spin_lock(&mm->page_table_lock); 2364 BUG_ON(!pmd_none(*pmd)); 2365 set_pmd_at(mm, address, pmd, _pmd); 2366 spin_unlock(&mm->page_table_lock); 2367 anon_vma_unlock(vma->anon_vma); 2368 goto out; 2369 } 2370 2371 /* 2372 * All pages are isolated and locked so anon_vma rmap 2373 * can't run anymore. 2374 */ 2375 anon_vma_unlock(vma->anon_vma); 2376 2377 __collapse_huge_page_copy(pte, new_page, vma, address, ptl); 2378 pte_unmap(pte); 2379 __SetPageUptodate(new_page); 2380 pgtable = pmd_pgtable(_pmd); 2381 2382 _pmd = mk_huge_pmd(new_page, vma); 2383 2384 /* 2385 * spin_lock() below is not the equivalent of smp_wmb(), so 2386 * this is needed to avoid the copy_huge_page writes to become 2387 * visible after the set_pmd_at() write. 2388 */ 2389 smp_wmb(); 2390 2391 spin_lock(&mm->page_table_lock); 2392 BUG_ON(!pmd_none(*pmd)); 2393 page_add_new_anon_rmap(new_page, vma, address); 2394 set_pmd_at(mm, address, pmd, _pmd); 2395 update_mmu_cache_pmd(vma, address, pmd); 2396 pgtable_trans_huge_deposit(mm, pgtable); 2397 spin_unlock(&mm->page_table_lock); 2398 2399 *hpage = NULL; 2400 2401 khugepaged_pages_collapsed++; 2402 out_up_write: 2403 up_write(&mm->mmap_sem); 2404 return; 2405 2406 out: 2407 mem_cgroup_uncharge_page(new_page); 2408 goto out_up_write; 2409 } 2410 2411 static int khugepaged_scan_pmd(struct mm_struct *mm, 2412 struct vm_area_struct *vma, 2413 unsigned long address, 2414 struct page **hpage) 2415 { 2416 pmd_t *pmd; 2417 pte_t *pte, *_pte; 2418 int ret = 0, referenced = 0, none = 0; 2419 struct page *page; 2420 unsigned long _address; 2421 spinlock_t *ptl; 2422 int node = -1; 2423 2424 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2425 2426 pmd = mm_find_pmd(mm, address); 2427 if (!pmd) 2428 goto out; 2429 if (pmd_trans_huge(*pmd)) 2430 goto out; 2431 2432 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2433 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2434 _pte++, _address += PAGE_SIZE) { 2435 pte_t pteval = *_pte; 2436 if (pte_none(pteval)) { 2437 if (++none <= khugepaged_max_ptes_none) 2438 continue; 2439 else 2440 goto out_unmap; 2441 } 2442 if (!pte_present(pteval) || !pte_write(pteval)) 2443 goto out_unmap; 2444 page = vm_normal_page(vma, _address, pteval); 2445 if (unlikely(!page)) 2446 goto out_unmap; 2447 /* 2448 * Chose the node of the first page. This could 2449 * be more sophisticated and look at more pages, 2450 * but isn't for now. 2451 */ 2452 if (node == -1) 2453 node = page_to_nid(page); 2454 VM_BUG_ON(PageCompound(page)); 2455 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2456 goto out_unmap; 2457 /* cannot use mapcount: can't collapse if there's a gup pin */ 2458 if (page_count(page) != 1) 2459 goto out_unmap; 2460 if (pte_young(pteval) || PageReferenced(page) || 2461 mmu_notifier_test_young(vma->vm_mm, address)) 2462 referenced = 1; 2463 } 2464 if (referenced) 2465 ret = 1; 2466 out_unmap: 2467 pte_unmap_unlock(pte, ptl); 2468 if (ret) 2469 /* collapse_huge_page will return with the mmap_sem released */ 2470 collapse_huge_page(mm, address, hpage, vma, node); 2471 out: 2472 return ret; 2473 } 2474 2475 static void collect_mm_slot(struct mm_slot *mm_slot) 2476 { 2477 struct mm_struct *mm = mm_slot->mm; 2478 2479 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2480 2481 if (khugepaged_test_exit(mm)) { 2482 /* free mm_slot */ 2483 hlist_del(&mm_slot->hash); 2484 list_del(&mm_slot->mm_node); 2485 2486 /* 2487 * Not strictly needed because the mm exited already. 2488 * 2489 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2490 */ 2491 2492 /* khugepaged_mm_lock actually not necessary for the below */ 2493 free_mm_slot(mm_slot); 2494 mmdrop(mm); 2495 } 2496 } 2497 2498 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2499 struct page **hpage) 2500 __releases(&khugepaged_mm_lock) 2501 __acquires(&khugepaged_mm_lock) 2502 { 2503 struct mm_slot *mm_slot; 2504 struct mm_struct *mm; 2505 struct vm_area_struct *vma; 2506 int progress = 0; 2507 2508 VM_BUG_ON(!pages); 2509 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2510 2511 if (khugepaged_scan.mm_slot) 2512 mm_slot = khugepaged_scan.mm_slot; 2513 else { 2514 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2515 struct mm_slot, mm_node); 2516 khugepaged_scan.address = 0; 2517 khugepaged_scan.mm_slot = mm_slot; 2518 } 2519 spin_unlock(&khugepaged_mm_lock); 2520 2521 mm = mm_slot->mm; 2522 down_read(&mm->mmap_sem); 2523 if (unlikely(khugepaged_test_exit(mm))) 2524 vma = NULL; 2525 else 2526 vma = find_vma(mm, khugepaged_scan.address); 2527 2528 progress++; 2529 for (; vma; vma = vma->vm_next) { 2530 unsigned long hstart, hend; 2531 2532 cond_resched(); 2533 if (unlikely(khugepaged_test_exit(mm))) { 2534 progress++; 2535 break; 2536 } 2537 if (!hugepage_vma_check(vma)) { 2538 skip: 2539 progress++; 2540 continue; 2541 } 2542 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2543 hend = vma->vm_end & HPAGE_PMD_MASK; 2544 if (hstart >= hend) 2545 goto skip; 2546 if (khugepaged_scan.address > hend) 2547 goto skip; 2548 if (khugepaged_scan.address < hstart) 2549 khugepaged_scan.address = hstart; 2550 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2551 2552 while (khugepaged_scan.address < hend) { 2553 int ret; 2554 cond_resched(); 2555 if (unlikely(khugepaged_test_exit(mm))) 2556 goto breakouterloop; 2557 2558 VM_BUG_ON(khugepaged_scan.address < hstart || 2559 khugepaged_scan.address + HPAGE_PMD_SIZE > 2560 hend); 2561 ret = khugepaged_scan_pmd(mm, vma, 2562 khugepaged_scan.address, 2563 hpage); 2564 /* move to next address */ 2565 khugepaged_scan.address += HPAGE_PMD_SIZE; 2566 progress += HPAGE_PMD_NR; 2567 if (ret) 2568 /* we released mmap_sem so break loop */ 2569 goto breakouterloop_mmap_sem; 2570 if (progress >= pages) 2571 goto breakouterloop; 2572 } 2573 } 2574 breakouterloop: 2575 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2576 breakouterloop_mmap_sem: 2577 2578 spin_lock(&khugepaged_mm_lock); 2579 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2580 /* 2581 * Release the current mm_slot if this mm is about to die, or 2582 * if we scanned all vmas of this mm. 2583 */ 2584 if (khugepaged_test_exit(mm) || !vma) { 2585 /* 2586 * Make sure that if mm_users is reaching zero while 2587 * khugepaged runs here, khugepaged_exit will find 2588 * mm_slot not pointing to the exiting mm. 2589 */ 2590 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2591 khugepaged_scan.mm_slot = list_entry( 2592 mm_slot->mm_node.next, 2593 struct mm_slot, mm_node); 2594 khugepaged_scan.address = 0; 2595 } else { 2596 khugepaged_scan.mm_slot = NULL; 2597 khugepaged_full_scans++; 2598 } 2599 2600 collect_mm_slot(mm_slot); 2601 } 2602 2603 return progress; 2604 } 2605 2606 static int khugepaged_has_work(void) 2607 { 2608 return !list_empty(&khugepaged_scan.mm_head) && 2609 khugepaged_enabled(); 2610 } 2611 2612 static int khugepaged_wait_event(void) 2613 { 2614 return !list_empty(&khugepaged_scan.mm_head) || 2615 kthread_should_stop(); 2616 } 2617 2618 static void khugepaged_do_scan(void) 2619 { 2620 struct page *hpage = NULL; 2621 unsigned int progress = 0, pass_through_head = 0; 2622 unsigned int pages = khugepaged_pages_to_scan; 2623 bool wait = true; 2624 2625 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2626 2627 while (progress < pages) { 2628 if (!khugepaged_prealloc_page(&hpage, &wait)) 2629 break; 2630 2631 cond_resched(); 2632 2633 if (unlikely(kthread_should_stop() || freezing(current))) 2634 break; 2635 2636 spin_lock(&khugepaged_mm_lock); 2637 if (!khugepaged_scan.mm_slot) 2638 pass_through_head++; 2639 if (khugepaged_has_work() && 2640 pass_through_head < 2) 2641 progress += khugepaged_scan_mm_slot(pages - progress, 2642 &hpage); 2643 else 2644 progress = pages; 2645 spin_unlock(&khugepaged_mm_lock); 2646 } 2647 2648 if (!IS_ERR_OR_NULL(hpage)) 2649 put_page(hpage); 2650 } 2651 2652 static void khugepaged_wait_work(void) 2653 { 2654 try_to_freeze(); 2655 2656 if (khugepaged_has_work()) { 2657 if (!khugepaged_scan_sleep_millisecs) 2658 return; 2659 2660 wait_event_freezable_timeout(khugepaged_wait, 2661 kthread_should_stop(), 2662 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2663 return; 2664 } 2665 2666 if (khugepaged_enabled()) 2667 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2668 } 2669 2670 static int khugepaged(void *none) 2671 { 2672 struct mm_slot *mm_slot; 2673 2674 set_freezable(); 2675 set_user_nice(current, 19); 2676 2677 while (!kthread_should_stop()) { 2678 khugepaged_do_scan(); 2679 khugepaged_wait_work(); 2680 } 2681 2682 spin_lock(&khugepaged_mm_lock); 2683 mm_slot = khugepaged_scan.mm_slot; 2684 khugepaged_scan.mm_slot = NULL; 2685 if (mm_slot) 2686 collect_mm_slot(mm_slot); 2687 spin_unlock(&khugepaged_mm_lock); 2688 return 0; 2689 } 2690 2691 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2692 unsigned long haddr, pmd_t *pmd) 2693 { 2694 struct mm_struct *mm = vma->vm_mm; 2695 pgtable_t pgtable; 2696 pmd_t _pmd; 2697 int i; 2698 2699 pmdp_clear_flush(vma, haddr, pmd); 2700 /* leave pmd empty until pte is filled */ 2701 2702 pgtable = pgtable_trans_huge_withdraw(mm); 2703 pmd_populate(mm, &_pmd, pgtable); 2704 2705 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2706 pte_t *pte, entry; 2707 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2708 entry = pte_mkspecial(entry); 2709 pte = pte_offset_map(&_pmd, haddr); 2710 VM_BUG_ON(!pte_none(*pte)); 2711 set_pte_at(mm, haddr, pte, entry); 2712 pte_unmap(pte); 2713 } 2714 smp_wmb(); /* make pte visible before pmd */ 2715 pmd_populate(mm, pmd, pgtable); 2716 put_huge_zero_page(); 2717 } 2718 2719 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, 2720 pmd_t *pmd) 2721 { 2722 struct page *page; 2723 struct mm_struct *mm = vma->vm_mm; 2724 unsigned long haddr = address & HPAGE_PMD_MASK; 2725 unsigned long mmun_start; /* For mmu_notifiers */ 2726 unsigned long mmun_end; /* For mmu_notifiers */ 2727 2728 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); 2729 2730 mmun_start = haddr; 2731 mmun_end = haddr + HPAGE_PMD_SIZE; 2732 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2733 spin_lock(&mm->page_table_lock); 2734 if (unlikely(!pmd_trans_huge(*pmd))) { 2735 spin_unlock(&mm->page_table_lock); 2736 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2737 return; 2738 } 2739 if (is_huge_zero_pmd(*pmd)) { 2740 __split_huge_zero_page_pmd(vma, haddr, pmd); 2741 spin_unlock(&mm->page_table_lock); 2742 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2743 return; 2744 } 2745 page = pmd_page(*pmd); 2746 VM_BUG_ON(!page_count(page)); 2747 get_page(page); 2748 spin_unlock(&mm->page_table_lock); 2749 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2750 2751 split_huge_page(page); 2752 2753 put_page(page); 2754 BUG_ON(pmd_trans_huge(*pmd)); 2755 } 2756 2757 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address, 2758 pmd_t *pmd) 2759 { 2760 struct vm_area_struct *vma; 2761 2762 vma = find_vma(mm, address); 2763 BUG_ON(vma == NULL); 2764 split_huge_page_pmd(vma, address, pmd); 2765 } 2766 2767 static void split_huge_page_address(struct mm_struct *mm, 2768 unsigned long address) 2769 { 2770 pmd_t *pmd; 2771 2772 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2773 2774 pmd = mm_find_pmd(mm, address); 2775 if (!pmd) 2776 return; 2777 /* 2778 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2779 * materialize from under us. 2780 */ 2781 split_huge_page_pmd_mm(mm, address, pmd); 2782 } 2783 2784 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2785 unsigned long start, 2786 unsigned long end, 2787 long adjust_next) 2788 { 2789 /* 2790 * If the new start address isn't hpage aligned and it could 2791 * previously contain an hugepage: check if we need to split 2792 * an huge pmd. 2793 */ 2794 if (start & ~HPAGE_PMD_MASK && 2795 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2796 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2797 split_huge_page_address(vma->vm_mm, start); 2798 2799 /* 2800 * If the new end address isn't hpage aligned and it could 2801 * previously contain an hugepage: check if we need to split 2802 * an huge pmd. 2803 */ 2804 if (end & ~HPAGE_PMD_MASK && 2805 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2806 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2807 split_huge_page_address(vma->vm_mm, end); 2808 2809 /* 2810 * If we're also updating the vma->vm_next->vm_start, if the new 2811 * vm_next->vm_start isn't page aligned and it could previously 2812 * contain an hugepage: check if we need to split an huge pmd. 2813 */ 2814 if (adjust_next > 0) { 2815 struct vm_area_struct *next = vma->vm_next; 2816 unsigned long nstart = next->vm_start; 2817 nstart += adjust_next << PAGE_SHIFT; 2818 if (nstart & ~HPAGE_PMD_MASK && 2819 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2820 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2821 split_huge_page_address(next->vm_mm, nstart); 2822 } 2823 } 2824